Method for creating a patterned concrete surface

ABSTRACT

A method for creating a patterned concrete surface with the aid of a concrete surface retarding agent. According to the invention, printing technique or an output technique is used to transfer the surface retarding agent forming the desired pattern to the surface coming into direct contact with the concrete to be cast. The printing or output technique can also be used to transfer a release agent or other substance affecting the surface of the concrete to the surface coming into contact with the concrete to be cast, in the same or in a separate transfer stage.

The present invention relates to a method for creating a patternedconcrete surface. The method provides innumerable possibilities forshaping the surface structure of concrete in formwork and castingtechniques. The method of the invention can be applied both when castingprefabricated units and in in-situ casting.

Previous use has been made of the surface retarding of concrete inconcrete formwork and casting techniques, to create an exposed-aggregateconcrete surface. Concrete surface retarding agents are existingsubstances, which retard the hardening of the concrete. They are used tocreate an exposed-aggregate concrete surface.

When casting prefabricated concrete units among other things, paper onwhich a surface retarding agent has been spread evenly is used on thebottom of the formwork, to create compact exposed-aggregate concreteunits.

A surface retarding agent is also apparently used in certainapplications, in such a way that the surface retarding agent is spreadmechanically by hand through some kind of stencil onto the bottom of theformwork, thus creating some individual image.

Methods also exist, by means of which patterned exposed-aggregateconcrete can be manufactured within predetermined limits, by using thesurface retarding agent technique. Two such methods, which havesomething in common with the present invention, are disclosed in detailin the following. However, the publications referred to are clearlytechnically and economically inferior to the present invention.

The idea of one method is disclosed in U.S. Pat. No. 4,055,322. In thismethod, the surface retarding agent is spread on a water permeablemembrane. The membrane is placed in the formwork, in such a way that thesurface retarding agent is directly against the formwork surface, andthe concrete is cast on top of the membrane. In order to function, thesurface retarding agent must travel through the membrane to the surfaceof the concrete by means of diffusion, aided by water that has bled fromthe concrete.

The weakness of this method is that the need for water permeabilitylimits the materials that can be used, on which the surface retardingagent is spread. In addition, the requirements of the fresh concretealso include a sufficient bleeding of water, which is difficult tocontrol. This is particularly the case in present concrete technology,in which precisely the concrete grades that ensure a long-termdurability feature a very small degree of water bleeding. On the otherhand, a permeable membrane also weakens the final result, as themovement of the retarding agent inside the membrane also in thedirection of the formwork is not taken into account in the patent andprobably cannot be prevented. Thus, there is no precise boundary betweenthe exposed and unexposed surfaces. Overall, it appears that the controlof the behaviour of the surface retarding agent in the method accordingto the patent referred to is decisively poorer than in the methodaccording to the patent now being applied for.

In practice, the formwork material immediately against the concrete onall smooth-cast concrete surfaces, made by the method according to U.S.Pat. No. 4,055,322, has been the water permeable membrane referred toabove. The membrane may have an undesirable, and at leastuncontrollable, effect on the quality of the smooth-cast surface.

The idea of the other method is disclosed in patent EP-0052237. In thismethod, a normal surface retarding agent membrane is used, with asurface treatment used to cover the part of the membrane on which anexposed-aggregate surface is not desired.

This method is uneconomical, in that a surface retarding agent membraneis required for the entire area to be patterned. In fact, thesmooth-cast surface has not only the membrane, but also two layers ofchemicals, i.e. the surface retarding agent and a varnish. In addition,the method referred to differs decisively form the present invention, inas much as only one surface retarding agent can be used at a time.

The present invention utilizes a surface retarding agent in an attemptto create a new concept, in which the surface retarding agent is appliedeither with a printing technique or an output technique.

The method now disclosed also provides, unlike its predecessors, anexcellent opportunity of influencing the properties of the smooth-castsurface now created. As is generally known, the release agent spread onthe surface of the formwork has its own effect on the quality of thesmooth-cast surface created. Several different release agents have beendeveloped to suit different formwork materials and grades of concrete.Release agents can be roughly divided into the following groups, forexample:

pure mineral oils

chemically modified vegetable oils

mixtures of vegetable and mineral oils

emulsified mineral oils

emulsified vegetable oils.

In the method now disclosed, a suitable release agent can be spread onparts of the membrane, on which the surface retarding agent is notspread. This creates the desired quality of smooth-cast surface.

Another advantages of this embodiment is that, in prefabricated units,in which there will be no patterning at all, it is sufficient to spreadthe same release agent as that used on the membrane onto the surface ofthe smooth formwork. The methods previously referred to have not hadthis advantage, instead, in both methods, if it is desired that thesurface of an entirely smooth-cast unit is identical with thesmooth-cast surface of a partly exposed-aggregate unit, membranes mustalso be spread on these units. Here too the concrete manufacturer cannotinfluence the quality of the smooth-cast surface.

The method according to the invention is intended to achieve a solutionwith the following properties:

1. the method can be used to create a new kind of surface treatment forconcrete in concrete casting technology, which allows the joints betweenunits and the various graphic relief surfaces to be taken into accountas part of the design

2. the method provides innumerable possibilities for the designer toshape the surface texture of the concrete with various graphic patterns

3. the method is as flexible as possible, and can be applied todifferent kinds of concrete casting

4. the point of departure of the method is the most designer-friendlyproduction possible. The designer may send the finished design over adata network to the factory where it will be produced

5. a central objective, concerning the runoff of rainwater and thedirtiness of city air, is to anticipate the dirtying of the facadealready during design

6. significant additional costs are avoided, compared to a conventionalconcrete surface.

The method is based on using concrete surface retarding agents, and, ifdesired release agents or other desired substances, either by printingtechniques or output techniques, in formwork and casting technology. Thedesired surface pattern is transferred to the casting surface of theformwork, either by printing techniques or output techniques, in which aconcrete surface retarding agent is used as the pigment. Modem printingand output techniques make it possible, if desired, the simultaneous orsequential addition of several different surface retarding agents orother substances, which have different effects on the concrete surface.This is because the basic principle of the invention includes not onlythe formation of a certain pattern, but also the surfacing of areas, towhich a surface retarding agent is not added, with a release agent orother substance affecting the concrete surface and, in turn, the qualityof the concrete piece created. The surface retarding agents may be oftypes that affect at different depths.

The casting surface of the formwork may be especially a membrane-likematerial, for example, coated paper or some other material, to which thepattern is transferred either by a printing or an output technique, inwhich a surface retarding agent acts as the printing agent or outputagent. The technique may be serigraphy, flexography, a digital outputtechnique, or any other printing or output technique. Once the castconcrete has hardened, the formwork is released and the concrete piecewashed, to form a pattern on the parts of the exposed-aggregate surface,in which the surface retarding agent was in the formwork.

The method has several advantages over previously known methods ofpatterning concrete surfaces. Known methods of creating patterns inprefabricated concrete units have included various profiles attached tothe bottom of the formwork, surface retarded spread with a brush throughsome stencil on the bottom of the formwork, sand-blasted patterns on thesurface of the concrete unit, or the mechanical grooving of the concreteunits. These previously known methods are largely manual processes andthus time-consuming and prevent less restricted patterns being createdon the concrete surface. Compared to the state of the art of thepublications referred to above, the method of the present invention ismore diverse, and economically and ecologically more rational.

The new method according to the invention permits more highly automatedproduction and innumerable possibilities for varying the patterns. Itcan be used to create a three-dimensional effect on the surface of aconcrete piece being manufactured, as the invention makes it easy tocreate various of depth effects, as disclosed later with reference tothe drawings and examples of embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is disclosed in detail with reference to the accompanyingdrawings, in which:

FIG. 1 shows one solution created according to the invention seen fromdirectly above;

FIG. 2 shows a cross section of the shape of a concrete piece obtainedby using the method according to the method; and

FIG. 3 shows a cross section A-A in FIG. 1.

In FIGS. 1, 2, and 3, the layers are drawn with a considerable thicknessfor reasons of clarity, without intending to show the actual thicknessof the layers. In practice, the layers are very thin. The aggregateparticles exposed on the surface of the concrete, which are central tothe final result, have intentionally not been shown in FIG. 2.

In the examples shown in the Figures, three surface retarding agentsthat retard to different wash depths are used, and are spread on thesurface by means of a printing or output technique. The referencenumbers 1, 2, and 3 mark these layers. The retarding agent marked by thenumber 1 retards the hardening of the concrete to the greatest depth, asshown in the profile in FIG. 2. The agent marked with the number 2 has amoderate effect while that with reference number 3 has the leastretarding effect.

As FIG. 1 shows, the patterns from the surface retarding agents areclear and in sharp outline. Thus, they also create a direct and sharplydrawn image. In the Figures, reference number 4 marks the release agent,which is added to the surface using the same technique as the surfaceretarding agent. Generally, the same work stage or sequential workstages can be used to add the various materials. In the same way, whenspreading different substances, an output technique can be used ifdesired with one substance and a printing technique with another. Atechnique may be selected because, for example, one substance is moreeasily spread with one technique and the other with another.

The essentially water impermeable membrane, to which substances 1, 2, 3,and 4 are transferred by a printing or output technique, is marked bynumber 5. Number 6 shows the formwork platen, on which the patternedsurface retarding agent membrane is placed. In FIG. 2, reference number7 refers to the concrete.

In the following, the method is disclosed with the aid of examples ofembodiments:

EMBODIMENT EXAMPLE 1 Serigraphy on a Membrane

The desired surface pattern is transferred to the membrane usingserigraphy, in which a concrete surface retarding agent is used as theprinting ink. This creates a patterned surface retarding agent membrane,with the concrete surface retarding agent forming the desired patternson the membrane. Serigraphy is an existing semiautomatic technique. Inserigraphy, the desired number of surface retarding agents, releaseagents, or other substances can be printed. At the concrete factory, thepatterned surface retarding agent membrane is spread on the bottom ofthe formwork and the concrete material is poured into the formwork. Oncethe concrete has hardened, the concrete unit is released from theformwork and its surface is washed. The pattern arises in these parts ofthe surface of the concrete, in which there has been surface retardingagent in the membrane.

Selecting the correct type of membrane prevents crumpling of the surfaceretarding agent membrane during the process and if desired, byperforating the base of the unit-casting formwork and connecting theholes thus formed to a vacuum reservoir. The vacuum holds the surfaceretarding agent membrane tightly onto the bottom of the formwork. Inin-situ casting, the patterned surface retarding agent membrane can beused according to the invention in such a way that an adhesive securesthe membrane to the casting surface of the formwork.

EMBODIMENT EXAMPLE 2 Flexography on a Membrane

The desired surface pattern is printed on the membrane with a flexographprinting press, using concrete surface retarding agent as the printingink. A flexograph printing press is a so-called roller printing press,in which the prepared printing plates are attached around the roller. Aflexograph printing press can print, depending on the machine, a3-5-meter impression and a repeating pattern up to three meters long. Aflexograph printing press can print in four colours in one and the samework stage. The flexograph technique is generally regarded as moreeconomical than serigraphy in larger print runs. In concrete casting, asurface retarding agent membrane printed by this technique is used inthe same way as in embodiment example 1.

EMBODIMENT EXAMPLE 3 Digital Output Technique

The desired surface pattern is programmed on a digital printer, whichcan print an impression up to 5 meters wide. The length of the outputimpression is not restricted, but can be as long as the file, so that,for example, a varying pattern 5 kilometers long can be output. Such adigital output printer can print on any material at all, because theprinting nozzles a well clear of the printing material. Such a printeris apparently used at least in the automobile industry, to meet ordersfor individually painted cars.

Concrete surface retarding agents and release agents are used asprinting inks when manufacturing a patterned surface retarding agentmembrane in a digital printer. These substances are formed to the sameviscosity as the colours normally used in the machine. The layerthickness of the substances to be printed can be adjusted digitally,without restriction. Such a digital printer prints the desired patterndigitally on the desired material. The printing material may be, forexample, a membrane impermeable to water, formwork plywood, or thebottom of the concrete unit formwork, which is generally stainlesssteel.

A surface retarding agent membrane output by this technique is used tocast a prefabricated concrete unit in the same way as in embodimentexample 1. Formwork plywood, which has been printed with concretesurface retarding agent patterns using this technique, can be used inin-situ casting. The bottom of formwork, which has been printed withconcrete surface retarding agent patterns using this technique, is usedin prefabricated concrete unit casting technology.

What is claimed is:
 1. A method for creating a patterned concretesurface, comprising the steps of providing a membrane, applying asurface retarding agent and a release agent to the membrane in a desiredpattern by means of a printing technique or an output technique, pouringconcrete material onto the membrane, permitting the concrete to harden,releasing the concrete, and processing the concrete to expose thedesired pattern, whereby the retarding agent and release agent aretransferred directly to the concrete to be cast.
 2. A method accordingto claim 1, wherein the surface retarding agent and release agent areapplied to the membrane by serigraphy, flexography, offset printing, ora digital output technique.
 3. A method according to claim 1, whereinthe membrane is made from a material selected from the group ofmaterials consisting of cellulose, plastic, or metal, and wherein themembrane is placed on the bottom of formwork, with the surface retardingagent and release agent pattern facing the concrete material to be cast.4. A method according to claim 1, characterized in that the desiredpattern to be created with the concrete surface retarding agent isformed at the bottom of the formwork.
 5. A method according to claim 1,characterized in that, after hardening, processing of the cast concretepiece is accomplished by washing off the concrete, the hardening ofwhich has been retarded to create the patterned concrete surface.
 6. Amethod according to claim 1, characterized in that plural surfaceretarding agents are applied, each acting at different depths withrespect to the cast concrete to form the patterned concrete surface. 7.A method of creating a patterned concrete surface, comprising the stepsof: (a) providing a water impermeable membrane having first and secondsides, (b) applying, by a printing process selected from the group ofprocesses consisting of serigraphy, flexography and digital output, tothe first side of the membrane, in a predetermined pattern: (i) asurface retarding agent, and (ii) a release agent, the release agent notbeing placed where the surface retarding agent is place, (c) placing themembrane in a form, with the first side of the membrane exposed, (d)pouring concrete material onto the first side of the membrane, (e)permitting the concrete to cure to predetermined level, (f) releasingthe cured concrete, and (g) processing the cured concrete by washing, toexpose the desired patterned concrete surface, whereby the surfaceretarding agent and release agent forming the predetermined pattern comeinto contact direct contact with and are transferred directly to theconcrete material to aid in forming the patterned concrete surface.